@AlanMunn -- asking you since you edited the question ... maybe "extend" the title to "how to look up a symbol or the style of a math alphabet"? many, many questions are about alphabet styles, not just other symbols, and this doesn't seem to be obvious.
–
barbara beetonJun 5 '13 at 12:59

13 Answers
13

You can look things up in the Comprehensive LaTeX symbols list. It can usually be easily accessed with texdoc symbols or texdoc symbols-a4 (in MiKTeX the latter only).

Another good option is to try the web-based software Detexify, which allows you to draw the symbol and tries to recognize what you've drawn. Here is a screenshot:

If you are using the package unicode-math, then besides using any Unicode character list, the list of all supported symbols (texdoc unimath-symbols) is very useful as it also lists which symbols are available in the various fonts.

The above techniques provide an adequate way of finding symbols but are not necessarily foolproof since you sometimes need to know what you're looking for in order to find it. For example, in Typing Following notation in Latex it may not be apparent that "vector fields in differential geometry" are somehow related to "bowties". To that end, searching for a symbol rotated 90 degrees or flipped horizontally, say, might lead you in the right direction.

+1, Detexify was a lifesaver for me, many times!
–
Amir RachumJul 26 '10 at 19:36

8

Yup, Detexify has become the best way to do this
–
Joseph Wright♦Jul 26 '10 at 19:38

4

Would you mind to change the link from "this website" to "Detexify"? Nice answer though!
–
Nils SchmidtJul 28 '10 at 22:59

8

Detexify is particularly useful if you get it on a device with a touch screen (there are Android/iPhone apps for it) -- personally, I find it rather difficult to draw with my mouse, but finger works fine :)
–
TJ EllisMay 31 '11 at 19:49

7

It's worth pointing out that the Select from the complete list! link in the results list will display the symbols list ordered by score, so it's more useful than the intimidating term complete list might suggest.
–
JakeOct 21 '11 at 6:25

Theres lots of ways of doing this, but the two I've found to be most useful are these:

Detexify Allows you to draw the symbol, and then guesses based on similar symbols. This is great for me because I don't always remember the name of the symbol, and even if I know the name, I may not have the correct name.

AMS LaTeX Short Math Guide This short pdf gives an overview of AMS LaTeX functionality, and includes a pretty thorough list of most of the math symbols (un)commonly used in proofs and formulas.

The new hotness is to use DeTeXify which uses handwriting recognition to look the symbol up for you.

DeTeXify even comes in an iPhone/Andriod app- you can get a free version or pay for one. The only difference is that with the paid app you are making a donation to the developer- the feature set is exactly the same.

The author is planning to work on a mobile version of the website that will supplant these apps.

For uncommon symbols, instead of search documentation on-line or in a big PDF to find packages and commands to include in my code, I have found useful sometimes to compile the whole table of characters of a font (even in the working document) to quickly find, for example, the skull of the omding font that is \char194. Of course, you have first to know that you have a font file with that name (omding.tfm) but then is easy:

You can also search for a skull the in Comprehensive LaTeX symbols list, or paint a skull in Detexify, or remember the easy command "\skull" (and do not forget load the skull package and enter in math mode) o try to find a \dingbat or \ding{whatever}... but when I want a skull (really never) must be that of white bones (just try the other methods if you don't know what I mean).

This reference has yet to fail me; it has all the symbols typeset along with the \foo command needed to generate them. There's also this PDF, which is considerably better put-together and covers other symbols besides the base math ones

TL;DR

This service allows classification by drawing (even works on mobile devices!) and by text:

Some information

The handwriting recognition toolkit (hwrt) is one possibility to classify you recordings. There are still many rough edges and the software gets updated on a daily basis (04.12.2014). The user interface is in a browser and looks like this:

The installation is explained in the documentation. If you have trouble or have an idea how to improve it, just leave a comment or write an email (info@martin-thoma.de).

@ moose I'm sorry but now error: package directory hwrt does not exist appears when I try to install by python setup.py install. Maybe it would be easier to provide a complete portable version for testing (without third party modules needed).
–
Tim S.Dec 17 '14 at 18:33

@TimS. Is this still a problem? Could we talk about it via email (info@martin-thoma.de) or via GitHub issue?
–
mooseApr 18 at 20:02

I use the Daum Equation editor then just copy and paste the code at the bottom (you can specify Tex,LaTeX, etc.) and even favourite the equations/symbols to avoid having to re-look them up every time you use them.
Not sure if they have EVERY symbol, but it has been a good reference for me so far!

In case you are using TeXstudio or Texmaker, you can browse the built-in catalog of symbols and find the symbol you need in the appropriate category of symbols (see the image below). It is very convenient, as by clicking on the symbol it gets automatically inserted into your document.

Moreover, if you're using TeXstudio on Windows, you can use Wizards -> Math Assistant... which enables you to draw symbols and it translates them into text.